[116.20] Galaxy structure: core radii and central mass deficits

We investigate the nuclear and global structure of
early-type galaxies, and the apparent disparity between the
Nuker and Sersic models for radial light profiles. We show
that the so-called "power-law" galaxies in fact have Sersic
r1/n profiles over their entire observed radial range.
Consequently, only three (Sersic-profile) parameters are
required to simultaneously describe both the inner
(HST-resolved) and outer profiles of low-luminosity (M >
-20.5 B-mag) elliptical galaxies. We also find that "core
galaxies" have Sersic profiles with a (partially evacuated)
single power-law core. We have developed a modified
(5-parameter) Sersic profile with a power-law core to model
the complete radial extent of luminous galaxies with cores.
In addition to quantifying the global stellar distribution
in these systems, we have derived new estimates of their
core radii (and central mass deficits) and compare these
with values obtained using the (5-parameter) Nuker model.

Support for proposal number HST-AR-09927.01-A was provided
by NASA through a grant from the Space Telescope Science
Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA
contract NAS5-26555.